[Structural Sharing] PR 1: Centralized key utilities with bidirectional indexes

[fabioh8010]

Details

First PR of Expensify/App#86181

Key-related functions are currently scattered across OnyxUtils and OnyxCache, and collection key lookups require O(C) linear scans over all collection keys. This PR extracts them into a new OnyxKeys module with two pre-computed maps:

• memberToCollectionKeyMap: member key → collection key (O(1) reverse lookup)
• collectionToMembersMap: collection key → Set of member keys (O(1) forward lookup)

Both maps are maintained incrementally as keys are added/removed from cache. The forward lookup is essential for PR 3's snapshot rebuild — it allows iterating only the members of the affected collection instead of scanning all keys. Pure refactor — no behavioral change.

E/App PR: Expensify/App#86201

Related Issues

Expensify/App#86181

Automated Tests

Unit tests were added.

Manual Tests

Since it's 99% refactor there isn't anything specific to test, just assert the app loads and doesn't crash. Use Expensify/App#86201 for testing.

1. Login with an account.
2. Navigate to Inbox tab.
3. Kill the app/refresh page and open app again.
4. Assert it loads correctly.

Author Checklist

• I linked the correct issue in the ### Related Issues section above
• I wrote clear testing steps that cover the changes made in this PR
  • I added steps for local testing in the Tests section
  • I tested this PR with a High Traffic account against the staging or production API to ensure there are no regressions (e.g. long loading states that impact usability).
• I included screenshots or videos for tests on all platforms
• I ran the tests on all platforms & verified they passed on:
  • Android / native
  • Android / Chrome
  • iOS / native
  • iOS / Safari
  • MacOS / Chrome / Safari
• I verified there are no console errors (if there's a console error not related to the PR, report it or open an issue for it to be fixed)
• I followed proper code patterns (see Reviewing the code)
  • I verified that any callback methods that were added or modified are named for what the method does and never what callback they handle (i.e. toggleReport and not onIconClick)
  • I verified that the left part of a conditional rendering a React component is a boolean and NOT a string, e.g. myBool && <MyComponent />.
  • I verified that comments were added to code that is not self explanatory
  • I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
  • I verified proper file naming conventions were followed for any new files or renamed files. All non-platform specific files are named after what they export and are not named "index.js". All platform-specific files are named for the platform the code supports as outlined in the README.
  • I verified the JSDocs style guidelines (in STYLE.md) were followed
• If a new code pattern is added I verified it was agreed to be used by multiple Expensify engineers
• I followed the guidelines as stated in the Review Guidelines
• I tested other components that can be impacted by my changes (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar are working as expected)
• I verified all code is DRY (the PR doesn't include any logic written more than once, with the exception of tests)
• I verified any variables that can be defined as constants (ie. in CONST.js or at the top of the file that uses the constant) are defined as such
• I verified that if a function's arguments changed that all usages have also been updated correctly
• If a new component is created I verified that:
  • A similar component doesn't exist in the codebase
  • All props are defined accurately and each prop has a /** comment above it */
  • The file is named correctly
  • The component has a clear name that is non-ambiguous and the purpose of the component can be inferred from the name alone
  • The only data being stored in the state is data necessary for rendering and nothing else
  • If we are not using the full Onyx data that we loaded, I've added the proper selector in order to ensure the component only re-renders when the data it is using changes
  • For Class Components, any internal methods passed to components event handlers are bound to this properly so there are no scoping issues (i.e. for onClick={this.submit} the method this.submit should be bound to this in the constructor)
  • Any internal methods bound to this are necessary to be bound (i.e. avoid this.submit = this.submit.bind(this); if this.submit is never passed to a component event handler like onClick)
  • All JSX used for rendering exists in the render method
  • The component has the minimum amount of code necessary for its purpose, and it is broken down into smaller components in order to separate concerns and functions
• If any new file was added I verified that:
  • The file has a description of what it does and/or why is needed at the top of the file if the code is not self explanatory
• If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
• If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.
• I have checked off every checkbox in the PR author checklist, including those that don't apply to this PR.

Screenshots/Videos

Android: Native

Screen.Recording.2026-03-25.at.08.30.46-compressed.mov

Android: mWeb Chrome

Android Chrome is always crashing for me so I can't test

iOS: Native

Screen.Recording.2026-03-25.at.08.38.48-compressed.mov

iOS: mWeb Safari

Screen.Recording.2026-03-25.at.08.40.05-compressed.mov

MacOS: Chrome / Safari

Screen.Recording.2026-03-25.at.08.41.19-compressed.mov

Screen.Recording.2026-03-25.at.08.43.21-compressed.mov

[fabioh8010]

Ready to review @Julesssss @tgolen

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🚀 Published to npm in 3.0.54 🎉